Text and Data Mining valid from 2018-07-24
Received: 9 January 2018
Accepted: 11 July 2018
First Online: 24 July 2018
Ethics approval and consent to participate
: Ethics approval for the study was granted by the Ethics Review Committee of Peking University, and all the participants provided signed informed consent at the time of participation. The study methodology was carried out in accordance with approved guidelines.
: Not applicable.
: The authors declare that there are no conflicts of interest.
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